Shadows along edges of mesh in 3D View
The issue you are calling "shadow along edges" is more generally known as z-fighting   (if you want to search for more info on the topic).

In our manual we document this problem:


  A large clipping range will allow you to see both near and far objects, but reduces the depth precision.


To resolve, in the view settings you need to reduce clipping range.


set the Clip Start as high as you can before near geometry disappears.
set the Clip End as low as you can before far geometry disappears.


The Camera has its own start/end settings so you may want to adjust that too.

Note that typically you won't need to tweak this value often, it just needs to match the scene scale you use

A range between 0.1 -> 100.0 is fine if more model has dimensions of ~0.5 -> ~50 blender-units.

Note that some graphics cards cards suffer from this problem more than others because they use a lower bit-depth for their z-buffer.